Heart and Stroke Encyclopedia

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An abdominal aortic aneurysm, also called aortic aneurysm, occurs when the large blood vessel (the aorta) that supplies blood to the abdomen, pelvis and legs becomes abnormally large or balloons outward. This type of aneurysm is most often found in men over age 60 who have at least one or more risk factor, including emphysema, family history, high blood pressure, high cholesterol, obesity and smoking.

Ablation, or cardiac ablation, is a therapeutic method used to destroy a small section of heart tissue causing abnormal electrical activity or irregular heartbeat. Ablation is done using electrodes that help identify the site of abnormal activity, then deliver either radiofrequency energy (RF ablation) or intense cold (cryoablation) to destroy the tissue.

Abnormal glucose tolerance is when the body is unable to break down, or metabolize, sugar adequately. The body uses a type of sugar called glucose for energy. People with abnormal glucose tolerance, also called impaired glucose tolerance, are considered prediabetics. They are at increased risk for developing type 2 diabetes, which is an important risk factor for heart disease and stroke.

ACE inhibitors, also called angiotensin-converting enzyme inhibitors, are drugs used to treat high blood pressure and heart failure. ACE inhibitors s alters the body's ability to produce angiotensin II, a hormone that causes the arteries to narrow. By blocking the making of angiotensin, these drugs help the blood vessels relax and widen, which lowers blood pressure, increases blood flow to the heart and reduces the heart's workload.

Actin is a protein that helps make up the structure of muscles in the heart. As muscle cells die during a heart attack, actin is released into the blood. A blood test to measure actin can help confirm a heart attack and determine the extent of heart damage.

Acute coronary syndrome is an umbrella term for when blood supplied to the heart muscle is decreased or blocked, leading to a heart attack. The common signs of acute coronary syndrome are chest pain or discomfort, which may involve pressure, tightness or fullness; pain or discomfort in one or both arms, the jaw, neck, back or stomach; shortness of breath; feeling dizzy or lightheaded; nausea; or sweating.

Adams-Stokes disease, also called Stokes-Adams disease, is a condition that leads to fainting (syncope) and sometimes convulsions. It happens when the electrical signals traveling from the upper to lower chambers of the heart are interrupted. This results in inadequate blood flow to the brain because the heart is beating too slowly (an arrhythmia called bradycardia).

Added sugar doesn’t contribute any nutrients to the diet and can lead to extra pounds and obesity, which hurts your heart health. Added sugar can be found in soft drinks, candy and a variety of other processed foods.

Adenosine is a substance produced by the body that plays a role in important biochemical processes. It causes increased blood flow to the heart muscle by relaxing the coronary arteries and other blood vessels in the body and regulates heart rhythm. Adenosine is also s a drug used to treat some types of arrhythmias (irregular heartbeats), specifically those that cause a fast heartbeat.

An automated external defibrillator is a computerized medical device that can check a person’s heart as well as shock it back to a normal rhythm. It can help save the life of someone who has suffered sudden cardiac arrest, the abrupt loss of heart function. The AED uses voice prompts, lights and text messages to tell the rescuer the steps to take. AEDs are very accurate and easy to use. With a few hours of training, anyone can learn to operate an AED safely.

Air pollution increases the risk for heart attack, stroke, heart failure, irregular heartbeats (arrhythmias) and cardiovascular death. Once inhaled, particulate matter can cause inflammation and irritate nerves in the lungs, starting a cascade of changes that adversely affect the rest of the body, including the heart. The elderly and people with existing heart diseases may be at higher risk from short-term exposure (hours or weeks). Long-term exposure further increases cardiovascular risk and reduces life expectancy, probably by several months to a few years. The American Heart Association recommends people, particularly those at high cardiovascular risk, limit their air pollution exposure.

Drinking large amounts of alcohol can increase the levels of some fats in the blood known as triglycerides and can lead to high blood pressure, heart failure and obesity. Excessive drinking and binge drinking can lead to stroke and sudden cardiac arrest. For those who consume alcohol, the American Heart Association recommends no more than two drinks per day for men and no more than one a day for women.

Alcohol abuse can lead to multiple medical complications, including stroke. Based on research examining alcohol and stroke risk, the American Heart Association recommends no more than two drinks per day for men and no more than one drink per day for non-pregnant women.

Aldosterone is a hormone produced by the adrenal glands. It regulates the balance of salt and water in the body by helping the kidneys retain sodium and excrete potassium. Aldosterone also acts on the central nervous system to increase a person’s appetite for salt and to make them thirsty. These effects directly control blood pressure and the balance of fluids in the blood.

Also called aldosterone receptor blockers, aldosterone antagonists block the body’s response to the hormone aldosterone, which normally causes the body to retain sodium and get rid of potassium. Aldosterone antagonists increase urination, thus reducing water and salt while retaining potassium. They help lower blood pressure, increase the heart’s pumping ability and help protect the heart in heart failure.

Also called aldosterone antagonists, aldosterone receptor blockers hinder the body’s response to the hormone aldosterone, which normally causes the body to retain sodium and get rid of potassium. Aldosterone receptor blockers increase urination, thus reducing water and salt while retaining potassium. They help lower blood pressure, increase the heart’s pumping ability and help protect the heart in heart failure.

Alpha-adrenergic antagonists are drugs used to lower blood pressure. They work by relaxing the muscles in the walls of blood vessels. With blood vessels open and relaxed, blood flow improves and blood pressure lowers. Alpha-adrenergic antagonists also lower blood pressure and reduce stress on the heart by slowing the heart rhythm and lessening the force of the heartbeat. These drugs are also called alpha blockers, alpha-adrenergic blocking agents and alpha-adrenergic blockers.

Alpha-adrenergic blockers are drugs used to lower blood pressure. They work by relaxing the muscles in the walls of blood vessels. With blood vessels open and relaxed, blood flow improves and blood pressure lowers. Alpha-adrenergic blockers also lower blood pressure and reduce stress on the heart by slowing the heart rhythm and lessening the force of the heartbeat. These drugs are also called alpha blockers, alpha-adrenergic antagonists and alpha-adrenergic blocking agents.

Alpha-adrenergic blocking agents are drugs used to lower blood pressure. They work by relaxing the muscles in the walls of blood vessels. With blood vessels open and relaxed, blood flow improves and blood pressure lowers. Alpha-adrenergic blocking agents also lower blood pressure and reduce stress on the heart by slowing the heart rhythm and lessening the force of the heartbeat. These drugs are also called alpha blockers, alpha-adrenergic antagonists and alpha-adrenergic blockers.

Alpha blockers are drugs used to lower blood pressure. They work by relaxing the muscles in the walls of blood vessels. With blood vessels open and relaxed, blood flow improves and blood pressure lowers. Alpha blockers also lower blood pressure and reduce stress on the heart by slowing the heart rhythm and lessening the force of the heartbeat. These drugs are also called alpha-adrenergic antagonists, alpha-adrenergic blocking agents and alpha-adrenergic blockers.

Ambulatory ECG, also called ambulatory electrocardiography, ambulatory EKG, or a Holter monitor, is a battery-operated, portable device that measures and tape-records the heart's electrical activity (ECG) continuously, usually for a period of 24 to 48 hours so that any irregular heart activity can be correlated with a person's activity. The device uses electrodes or small conducting patches placed on the chest and attached to a small recording monitor that is carried in a pocket or in a small pouch worn around the neck.

Ambulatory EKG, also called ambulatory ECG, ambulatory electrocardiography, or a Holter monitor, is a battery-operated, portable device that measures and tape-records the heart's electrical activity (ECG) continuously, usually for a period of 24 to 48 hours so that any irregular heart activity can be correlated with a person's activity. The device uses electrodes or small conducting patches placed on the chest and attached to a small recording monitor that is carried in a pocket or in a small pouch worn around the neck.

Ambulatory electrocardiography, also called ambulatory ECG, ambulatory EKG, or a Holter monitor, is a battery-operated, portable device that measures and tape-records the heart's electrical activity (ECG) continuously, usually for a period of 24 to 48 hours so that any irregular heart activity can be correlated with a person's activity. The device uses electrodes or small conducting patches placed on the chest and attached to a small recording monitor that is carried in a pocket or in a small pouch worn around the neck.

Amiodarone is a drug used to slow the heart rate and help keep it in a regular rhythm. It is used to treat fast or other irregular heartbeats, called arrhythmias, including atrial fibrillation, ventricular tachycardia and ventricular fibrillation. Amiodarone belongs to a class of drugs called antiarrhythmics. Side effects are usually dose-related and regular follow-up is necessary to evaluate kidney, liver and lung function.

An aneurysm is an abnormal weakening or ballooning-out of a vessel wall of an artery. Weakening of the blood vessel wall may be due to disease, injury or an abnormality present at birth. Some common locations for aneurysms include the aorta (the major artery leading away from the heart), the brain (called a cerebral aneurysm), leg, intestine and splenic artery (which supplies blood to the spleen).

Angina is chest pain or discomfort due to coronary heart disease. It occurs when the heart muscle doesn’t get as much blood as it needs. This usually happens because one or more of the heart’s arteries is narrowed or blocked, also called ischemia. Stable angina refers to “predictable” chest discomfort associated with exertion or stress. Unstable angina refers to unexpected chest pain and usually occurs at rest. It is typically more severe and prolonged. Unstable angina should be treated as an emergency.

Prinzmetal angina can also be called, variant angina, Prinzmetal's variant angina, angina inversa. Unlike typical angina – which is often triggered by exertion or emotional stress - Prinzmetal’s angina almost always occurs when a person is at rest, usually between midnight and early morning. These attacks can be very painful. The pain from variant angina is caused by a spasm in the coronary arteries (which supply blood to the heart muscle).

The spasms tend to come in cycles – appearing for a time, then going away. After six to 12 months of treatment, doctors may gradually reduce the medication.

Also called angina, angina pectoris is the medical term for chest pain or discomfort due to coronary heart disease. Angina pectoris occurs when the heart muscle doesn’t get as much blood as it needs. This usually happens because one or more of the heart’s arteries is narrowed or blocked, also called ischemia. Stable angina refers to “predictable” chest discomfort associated with physical exertion or mental or emotional stress. Unstable angina refers to unexpected chest pain and usually occurs at rest. It is typically more severe and prolonged. Unstable angina should be treated as an emergency.

Angioplasty, also known as percutaneous intervention, is a procedure in which a thin tube called a catheter is threaded into the heart with a deflated balloon at the tip. The balloon is then inflated to open spots where blood flow has been reduced or blocked. While doing an angioplasty, doctors may also implant a mesh tube called a stent to help prop open the artery, reducing the chance of another blockage. Another type of angioplasty is a laser angioplasty; instead of a balloon, the catheter carries a laser tip that sends pulsating beams of light to clear blockages.

Angiotensin is a hormone produced by the body that causes the blood vessels to narrow. Angiotensin acts as a vasoconstrictor, causing the smooth muscle cells within the blood vessels to constrict, thereby causing the blood pressure to go up.

Angiotensin-converting enzyme inhibitors, also called ACE inhibitors, are drugs used to treat high blood pressure and heart failure. ACE inhibitors s alters the body's ability to produce angiotensin II, a hormone that causes the arteries to narrow. By blocking the making of angiotensin, these drugs help the blood vessels relax and widen, which lowers blood pressure, increases blood flow to the heart and reduces the heart's workload.

Angiotensin II receptor blockers, also known as ARB blockers or angiotensin 2 receptor blockers, are drugs used to treat high blood pressure and heart failure. They do not interfere with the body's production of angiotensin. Instead, they block the effects of angiotensin, preventing the hormone from narrowing the blood vessels. By relaxing the coronary arteries, blood flow to the heart increases, blood pressure goes down and the heart's workload is reduced. Angiotensin II receptor blockers are often used in patients who cannot tolerate a common type of drugs known as ACE inhibitors.

The ankle-brachial index test is a painless exam that compares the blood pressure in the feet to the blood pressure in the arms to determine how well blood is flowing. This test is used to diagnose peripheral artery disease, or PAD, a condition that most often affects blood flow to the legs. The ankle-brachial index test takes only a few minutes and can be performed by a healthcare professional as part of a routine exam.

Antiarrhythmic medication helps control and slow the heart rate. Antiarrhythmics work by either slowing the activity of tissue that is initiating electrical impulses too quickly in the heart's natural pacemaker or by slowing the transmission of fast electrical impulses that cause the heart to beat. Antiarrhythmics include several classes of drugs, such as sodium channel blockers, beta-blockers, potassium channel blockers and calcium channel blockers. Other medications used to control heart rate include adenosine and digitalis (also called digoxin and digitoxin). The type of arrhythmia you have determines which medication is prescribed.

Antibiotic prophylaxis refers to the use of antibiotics before certain dental and medical procedures to prevent endocarditis, an infection caused by bacteria that enters the bloodstream and settles in the heart lining, a heart valve or a blood vessel. The American Heart Association recommends antibiotic prophylaxis only for patients at the highest risk for endocarditis.

Anticoagulants are drugs that decrease the ability of the blood to clot, or coagulate. Also called blood thinners, they are used to treat certain blood vessel, and heart and lung conditions. They are also given to some people at high risk for blood clots, including those with atrial fibrillation or artificial heart valves. Anticoagulants do not dissolve clots but may prevent existing clots from becoming larger and causing more serious problems. They are often prescribed to prevent first or recurrent heart attack or stroke. Common anticoagulant drugs are heparin, warfarin, rivaroxaban, apixaban, edoxaban and dabigatran.

Antihypertensive drugs are commonly prescribed to help lower blood pressure in conjunction with a heart-healthy diet and regular physical activity. Blood pressure-lowering drugs include diuretics, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, vasodilators, alpha blockers, beta-blockers, calcium channel blockers and central agonists. Many patients may require more than one drug to control high blood pressure. Some drugs used in hypertensive people may also be prescribed for heart failure and arrhythmia patients.

Antioxidants are natural substances found vitamins and minerals that are believed to help prevent disease by fighting free radicals, which are substances that can harm the body. Examples of free radicals are environmental contaminants such as cigarette smoke. Without adequate amounts of antioxidants, these free radicals can damage cells which can lead to the development of heart disease.

Antiplatelet agents are drugs used to prevent blood platelets from sticking together and forming blood clots. The drugs prevent clotting in patients who have had a heart attack, unstable angina, ischemic stroke, transient ischemic attack (also known as a warning stroke) or other form of cardiovascular disease. Common antiplatelet agents include aspirin, clopidogrel, dipyridamole, prasugrel, and ticagrelor.

An aortic aneurysm, also called abdominal aortic aneurysm, occurs when the large blood vessel (the aorta) that supplies blood to the abdomen, pelvis and legs becomes abnormally large or balloons outward. This type of aneurysm is most often found in men over age 60 who have at least one or more risk factor, including emphysema, family history, high blood pressure, high cholesterol, obesity and smoking.

Aortic dissection is a life-threatening condition that occurs when blood leaks from the aorta, the major artery that carries blood from the heart to the body. The leak is often caused by a tear in the inside wall of the aorta. The most common symptom of aortic dissection is sudden and severe chest pain or upper back pain.

Also called aortic valve regurgitation, aortic regurgitation is a condition in which the aortic valve does not close properly between each heartbeat. This causes some of the blood that was being pumped out of the heart to leak back into the heart. It typically takes a prolonged period of time for a person to develop symptoms, which may include fatigue and shortness of breath.

Also called aortic regurgitation, aortic valve regurgitation is a condition in which the aortic valve does not close properly between each heartbeat. This causes some of the blood that was being pumped out of the heart to leak back into the heart. It typically takes a prolonged period of time for a person to develop symptoms, which may include fatigue and shortness of breath.

Aortic stenosis, also known as aortic valve stenosis, occurs when the aortic valve inside the heart develops a narrow opening that impedes blood flow to the entire body. Symptoms of aortic stenosis can include shortness of breath and fainting.

Aphasia is the total or partial loss of the ability to use words. It may be caused by brain injury or disease, but most often it’s caused by a stroke that injures the brain's language center. Sometimes recovery is quick and complete after a stroke, but in other cases there may be permanent speech and language problems.

Angiotensin II receptor blockers, also known as ARB blockers or angiotensin 2 receptor blockers, are drugs used to treat high blood pressure and heart failure. They do not interfere with the body's production of angiotensin. Instead, they block the effects of angiotensin, preventing the hormone from narrowing the blood vessels. By relaxing the coronary arteries, blood flow to the heart increases, blood pressure goes down and the heart's workload is reduced. Angiotensin II receptor blockers are often used in patients who cannot tolerate a common type of drugs known as ACE inhibitors.

An arrhythmia is an abnormal heart rhythm that, when severe or long-lasting, can prevent the heart from pumping enough blood to the body. Damage to the heart muscle from a heart attack can make someone prone to arrhythmias, as can some congenital heart conditions. A variety of minerals, such as potassium, magnesium and calcium, with high or low concentrations in the blood and tissue can cause arrhythmias. So can alcohol, cigarettes and recreational drugs.

An arterial switch operation is an open-heart procedure. It is used to correct many forms of transposition of the great arteries, a congenital heart defect in which the aorta and the pulmonary artery are reversed. The surgery switches the two arteries back to their normal positions so the aorta is connected to the left ventricle and the pulmonary artery is connected to the right ventricle. The coronary arteries that carry oxygen-rich blood to nourish the heart muscle also must be re-attached to the new aorta.

Arteriography is a test in which a dye visible to X-rays is injected into the bloodstream. X-ray pictures then are studied to see if the arteries are damaged, narrowed or blocked. Arteriography is done during cardiac catheterization. It's also known as angiocardiography, angiogram and angiography.

Commonly called hardening of the arteries, arteriosclerosis includes a variety of conditions that cause artery walls to thicken and lose elasticity. It can occur because of fatty deposits on the inner lining of arteries, calcification of the wall of the arteries or thickening of the muscular wall of the arteries from chronically elevated blood pressure. It is also associated with aging.

Aspirin can help prevent blood clots from forming and is often used to prevent recurrent heart attacks and strokes. The American Heart Association recommends that people at high risk of heart attack take a daily low dose of aspirin, as instructed by their healthcare provider. Heart attack survivors often take a regular low dose of aspirin. Taking an aspirin can also help when a heart attack is in progress, greatly improving chances of survival.

Also called hypertrophic cardiomyopathy, asymmetric septal hypertrophy is a condition that occurs when heart muscles cells enlarge, causing the walls of the lower heart chambers (typically the left ventricle) to become thick and stiff. This makes it difficult for the heart to relax and for a sufficient amount of blood to fill the heart chambers. While the heart squeezes normally, the limited filling prevents the heart from pumping enough blood, especially during physical activity. Children with asymmetric septal hypertrophy are not allowed to play competitive sports because of the possibility of a sudden collapse or increased heart failure.

Asystole is a life-threatening heart rhythm characterized by an absence of electrical activity. Because there is no electrical activity, there is no heartbeat. This condition can lead to death if it's not treated and reversed immediately.

An atherectomy is a procedure to remove plaque from arteries. An ultra-thin wire is threaded through a special catheter into the blocked artery. Several devices may then be used: a high-speed rotating "burr" that grinds the plaque into tiny pieces; a small rotating cutter that "shaves off" pieces of the blockage; or a laser catheter that vaporizes the plaque.

Atherosclerosis is a form of arteriosclerosis in which the inner layers of artery walls become thick and irregular because of deposits of fat, cholesterol and other substances. This buildup is called plaque and can cause arteries to narrow, reducing the blood flow through them. Eventually plaque can erode the wall of the artery and diminish its elasticity. Plaque deposits can rupture, causing blood clots to form at the rupture that can block blood flow or break off and travel to another part of the body. This is a common cause of heart attack or ischemic stroke.

The atria are the heart's two upper chambers that receive and pump blood into the ventricles, the lower chambers of the heart. There are two atria, one on the right side of the heart and one on the left.

Atrial fibrillation is a disorder of heart rate and rhythm. Also commonly abbreviated as AF or Afib, it occurs when the heart's two small, upper chambers (atria) quiver rapidly and empty blood into the heart's lower chambers (ventricles) in a disorganized manner instead of beating effectively. Blood that isn't pumped completely out of the atria when the heart beats may pool and clot. If a piece of a clot enters the bloodstream, it may lodge in the brain causing a stroke. Causes of atrial fibrillation include dysfunction of the sinus node (the heart's pacemaking area in the right atrium), coronary artery disease, rheumatic heart disease, hypertension and hyperthyroidism.

An atrial flutter is a very rapid beating of the heart's upper chambers, or atria. It typically is not a stable rhythm and may lead to atrial fibrillation. Atrial flutter occurs most often in people with heart diseases such as pericarditis, coronary artery disease and cardiomyopathy.

The atrioventricular node, or AV node, is one of the major parts of the cardiac electrical conduction system, which controls heart rate and rhythm. This system generates electrical impulses and conducts them throughout the heart, stimulating the heart to contract and pump blood. Electrical impulses begin in the sinoatrial node and move down until reaching the AV node, a cluster of cells at the bottom of the heart’s right upper chamber. The AV node serves as a sort of electrical relay station that slows the current before the signal passes to the lower chambers.

An automated external defibrillator is a computerized medical device that can check a person’s heart as well as shock it back to a normal rhythm. It can help save the life of someone who has suffered sudden cardiac arrest, the abrupt loss of heart function. The AED uses voice prompts, lights and text messages to tell the rescuer the steps to take. AEDs are very accurate and easy to use. With a few hours of training, anyone can learn to operate an AED safely.

Also called an implantable cardioverter defibrillator, an automated internal defibrillator is a small battery-powered device that treats life-threatening irregular heartbeats (arrhythmias), including those that cause sudden cardiac arrest. The device is implanted under the skin of the chest with wires that connect to the heart. If the device detects an irregular heart rhythm, it sends electrical impulses to restore a normal rhythm.

Autonomic failure is a condition that occurs when the autonomic nervous system fails to function properly. Because the autonomic nervous system controls blood pressure and heart rate, autonomic failure can cause a rapid drop in blood pressure when standing. It can affect people with diabetes, degenerative neurological diseases and other conditions.

*All health/medical information on this website has been reviewed and approved by the American Heart Association, based on scientific research and American Heart Association guidelines. Use this link for more information on our content editorial process.